Present 3D imaging methods and associated devices have numerous disadvantages. In laser-based systems and devices using structured illumination, high accuracies in the range of a few micrometers or even less are possible. In exchange, the systems are quite technically complicated and thus costly and also sometimes slow. The light time-of-flight method is more cost-effective, but has heretofore not been able to offer correspondingly high measurement accuracies, they are at best in the millimeter range here.
A depth image camera is known from DE 10 2013 207 148, which suppresses interfering light reflections by using polarization filters and thus increases the measurement accuracy. The resulting measurement accuracy is still comparatively low, however.
It is known in principle that the polarization properties of the light reflected from a surface enable inferences about the type of the reflection and the structure of the reflective surface (see, for example, GB 2 515 000 A1). This can be explained because depending on the angle of incidence of the incident light in relation to the surface normal of the irradiated object, sometimes all polarization states cannot all be reflected uniformly, which results in a partial polarization in the reflected light. This fact can be explained in that the reflection of light as an electromagnetic wave is dependent in particular on the movement of the electrons in the reflecting material. For certain angles of incidence and thus angles of reflection, these electrons oscillate along the emission direction. In this case, light cannot be emitted, since the nature of light to form a transverse wave has to be fulfilled.
Furthermore, methods are known in which the polarization properties of the light are recorded with the aid of a polarimeter (see, for example, US 2016/0146937 A1).
In summary, the following disadvantages occur in the prior art:                inadequate measurement accuracy in light time-of-flight systems;        expensive components; and        large space requirement if polarimeters are used.        